Color stabilizer for oils



Patented Feb. 23, 1943 COLOR STABILIZER FOR OIES Melvin A. Dietrich,Claymont, DeL, assignor to- E. I. du Pont de Nemours & Company,Wilmington, DeL, a corporation of Delaware No Drawing. Application July23, 1940, Serial No. 346,987

12 Claims.

particularly to the color stabilization of viscous petroleum oils.

It is well known that mineral oils tend to deteriorate in color andgeneral appearance on exposure to the action of heat and light. It ishighly desirable to provide products which will retain their color andsatisfactory appearance over substantial periods of time. Numerousmaterials have been proposed for stabilizing mineral oils againstdeterioration in color. I have found new materials whichare particularlyeffective for preventing deterioration in color of mineral oils.

It is an object of the present invention to pro- ,vide new viscousmineral oil products which are more stable with respect to deteriorationin color and appearance than those. known heretofore. Another object isto provide a method for inhibiting deterioration in color of viscousmineral oils. A further object is to provide a class of compounds to beadded to viscous petroleum oils and which, when so added, will inhibitthe deteriorationin color of such oils. Still further objects are toprovide new compositions of matter and to advance the art. Other objectswill appear hereinafter.

The above and other objects may be accomplished in accordance-with myinvention which comprises incorporating in viscous petroleum oils smallproportions of oil soluble compounds of the group of esters and amidesof organic acids having two beta-amino-crotonic acid residues linkedthrough the beta-amino. nitrogen atoms to separate carbon atoms of asingle divalent aliphatic radical which are free of acidic substituents,that is, having no acidic groups other than that of the crotonic acid.Such compounds may be represented by the formula to the carbon of theC=O group and otherwise consists of carbon and hydrogen. As shown by theabove formula, it is believed that my compounds probably exist inequilibrium in two forms in a manner similar to the keto-enol forms ofacetoacetic ester and the formulae, as given, represent suchequilibrium. Since the crotonic structure is usually assigned to thistype of compound in the literature, I have employed the correspondingnomenclature herein. I have found that, when such compounds areincorporated in viscous petroleum oils, they are very effective ininhibiting deterioration in color of such oils.

By the term viscous petroleum 'oils, I mean oils of petroleum origin,including cracked, reformed and polymerized products, as well as thestraight run distillates, which oils boil above the kerosene range andpreferably have a viscosity of at least 35 seconds Saybolt Universal at100 F. Amongst such oils, I intend to include Diesel oils, gas oils,furnace oils, white oils and greases, as well as the usual lubricatingoils, but to exclude the substantially non-viscous products such asgasoline, kerosene and the like.

By the term "alkylene as used hereinafter, I mean divalent aliphatichydrocarbon radicals in which each valence is on a difierent carbonatom. By the terms beta-amino-crotonic acids and a beta-amino-crotonic'acid, I intend to include beta-amino-crotonic acid itself'and itshomologs in which the amino and carboxyl groups are 011 adjacentaliphatic carbon atoms and which are obtained by condensing abeta-ketonic acid with an amine, so that the oxygen of the keto group issplit off and replaced with an amino nitrogen. By anN,N'-alkylene-di(beta-amino-crotonic) acid, 'I mean such compounds inwhich the amine is an alkylene diamine which has been condensed with twomols of the beta-keto acid so that one, and only one, beta-keto acidgroup is of the aliphatic group, R represents hydrogen or a hydrocarbonradical, R" represents a hydrocarbon radical and X an organic groupcontaining a single oxygen or nitrogen directly bonded condensed witheach nitrogen ofthe alkylene diamine. By the term unsubstitutedN,N'-alkylene-di(beta-amino-crotonic) acid, I mean to include only thosecompounds in which the betaamino-crotonic acid group is that ofbeta-aminocrotonic acid itself and not of its homologs and in which thealkylene radical is a hydrocarbon radical; that is, to include onlythose compounds in which R represents hydrogen, R" represents a methylradical and A consists of carbon and hydrogen.

While the broad class of compounds will be efiective for my purpose, Ihave found that some of the most desirable compounds are the esters N,N'propylene difethyl beta amino-cro-' N,N' propylene di(butyl betaamino-crotonate) HaG- N,N ethylene di(ethyl beta amino-crotonate)HN-CHr-CHz-NH N,N' hexamethylene di(ethyl beta-aminocrotonate) NJTLO:31.10

N,N' (beta,beta' 1,4 diethylpheny1ene)-di- (ethyl-beta-amino-crotonate)N,N' (3,6 dioxa-octamethylene) di (ethylbeta-amino-crotonate) N,N' -(2hydroxy trimethylene) di (ethylbeta-amino-crotonate) Y N,I l' (3,6 diazaoctamethylene) di-ethylbeta-amino-crotonate) HN-C Hr-C Hz-NH-CHz- CHz-NHeCHz-CIIz-NH 0 0 The compounds of my invention may be employed inoils in concentrations ranging from about 0.02% to about 2% by weight.Preferably, only from about 0.02% to about 0.5% will be employed, sincethis is usually suflicient to impart satisfactory color stability. Ipreferably employ the pure compounds, but mixtures may also be used, orthe reactants may be added to the oil and the stabilizers produced insitu. They may be employed in the presence of other addition agentswhich areadded to improve service performance, such. as pour-pointdepressants, metal deactivators, corrosion inhibitors, gum solvents,viscosity index improving agents and materials to increase lubricity.

A naphthenic base oil of SAE ffl grade was used in evaluating the colorstabilizing action of the various esters. Fifty grams of oil wasplacedin 250 cc. beakers and heated at 300 F. for 6 hours in air in awell agitated oil bath. Color changes were measured on the A. S. T.MAInion colorim-' eter. In this, instrument, low readings indicatelight-colored oils while high readings show darkenediamine andpropylenediamine, respectively.

Brief descriptions of the preparation of representative compounds aregiven in the following examples to illustrate their preparation.

EXALJPLE 1 Twenty-six grams of ethyl acetoacetate, dissolved in 75 cc.of absolute alcohol, was-mixed with a solution of 11.6 gramshexamethylenediamine in 25 cc. alcohol. The mixture became warm and wasallowed to stand for a few hours. It was then carefully evaporated on asteam bath, a. pale yellow liquid remaining which weighed 33 grams. Thiswas crystallized from petroleum ether, the crystalline product boiledwith toluene,

containing a crystal of iodine, and the resulting product crystallizedfrom benzene, The final material was a white solid, melting at 69-70 C.,and having a nitrogen content of 8.06% compared to a calculated value of8.23%. pound was N,N-hexamethylene-di(ethyl betaamino-crotonate). I

The corresponding ethylenediamine derivative was made in the same mannerand melted at 125 C.

EXAMPLE 2 PREPARATION or- N,N'-r!:oPYm sE-nr(Eran-BETA-' AMIXOCRUTOSATE)Sixty-five parts by weight of ethyl acetoacetate. dissolved in cc.absolute alcohol,- were mixed with 22 parts of 35.8% propylenediaminedis- This comsolved in 50 cc. absolute alcohol. The mixture became warmand, after standing one hour, was evaporated on a steam bath. It wasthen taken up in benzene, dried over anhydrous sodium sulfate, and thesolvent removed by evaporation. The residue was a viscous red liquid,weighing '10 grams, and having a nitrogen content of 10.15%.

The product was also prepared by direct mixing of the two components,using no solvent, in the following manner. weight of ethyl acetoacetateand 8.6 parts of 85.8% propyenediamine were mixed by dropping thediamine into the ester. The mixture became warm but, on cooling in anice bath, became cloudy and separated into two layers. After standingovernight, the lower layer (water) was removed and the. upper layerdried with anhydrous magnesium sulfate. A yield of 27 grams of a yellowoil was obtained, having a nitrogen content of 9.61%. This product waslighter colored than the preceding material, the difference being due tothe length of time the material was exposed to heating during itsisolation.

EXAMPLE 3 Paaraaarrox or N,N'-PROPYLENE-DI(BUTYL-BETA- AMINOCBOTONATE)TABLE I Color stabilizing 'efiect of N,N'-ethylene-di-(ethyl-beta-amino-crotonate) (Naphthenic base S. A. E. 30 oil used,original color 2% Color Concentration of stabilizer-Percent iggg Color yweight heating increase test- None-control 5+ 2y 0.02 3 1 0.05 c 3+fi-i- 0.10 3+ t+ TABLE II Color stabilizing effect ofN,N'-hemamethylenedz (ethyl-beta-amino-crotonate) (Naphthenic base 8. A.E. 30 oil used. original'ooior 2%) Twenty-six parts by TABLE III Colorstabilizing efiect of. N,N' promllene,-di-,

(ethyl-beta-amino-crotonate) color units Concentration of sta- A. S. T.M. color True color Percent $23, Pemnt by amitest after test inhibition5 Dil. 1010 4 Dil. 554 58 7% 251 79 7+ 207 84 1 True color in the abovetable is measured in arbitrary units which have no scientificsignificance but which are useful for comparative pur ses.

I 11 these cases the color was so dark that it was necessary to dilutethe test samples in order to obtain accurate readings.

The above tests illustrate the stabilizing action ofa1kylenediamlne-acetoacetic ester products. The relatedalkylenediamine-acetoacetamide derivatives will also exert a stabilizingaction. This may be demonstrated through use ofN,N'-ethylene-di(beta-amino-crotonanilide) The N,N'ethylene-d1(beta-amino-crotonanilide) was prepared as follows: 8.6 gramsof 69.8% ethylenediamine and 35.4 grams of acetoacetani- Iide weredissolved in 150 cc. of absolute alcohol. After about 10 minutes; thesolution became warm spontaneously and a white crystalline precipitateformed. After standing several hours, the precipitate was separated byfiltration and crystallized from acetone. Forty-one grams of productwere obtained, melting at 200 to 201 C.

Two-tenths per cent of this last compound was dissolved in 20 grains ofa naphthenic base SAE 30 oil and heated, together with a control samplein cc. beakers to 160 to 165 C. for six hours. The colors of the heatedoil samples were then compared with the original oil in a' Duboscqcolorimeter. The results of the tests are as follows:

I Per cent color increase Untreated oilcontrol 520 Treated oil 208 9.80grams of 1,4-bis(beta-aminoethyl) benzene and 15.6 grams of ethylacetoacetate were mixed by dropping the melted amine onto the ester. Themixture became warm and cloudy. After standing a short time, benzene wasadded'and the solution allowed to stand over night. This was then washedwith water, dried over sodium sulfate, and the solvent removed over asteam bath. Seventeen grams of a cream colored solid were obtained,which, upon crystallization from ethyl alcohol, melted at 94-95? C. Theproduct has the structure were measured on a Duboscq colorimeter and14.8 grams of triglycoldiamine and 26 grams Tun IV of ethylacetoacetatewere mixed as in the pre- Per cent ceding example and worked up in thesame Compound: color inhibition fashion. A deep red liquid weighing 33grams N,N'-ethylene-d1(ethyl-beta-aminp-crowas obtained which hasthefollowing structure: tonate) 92021350-8-CH=CNHCH1-CH:OCH1CHrO-CH:-CHr'-NHC=CH- OCzHs CH: g I H)N,N'-iiipdioxa-octamcthyleneydi-(ethyl-beta-amlnmctonate) 9.1 grams of1,3-diaminopropanol-2 and 26 N,N'- hexamethylene-di(ethyl-beta-amigramsof ethyl acetoacetate were mixed as in the no-crotonate) 91 precedingexample .and worked up in the same Tetrabutyl ethylenediamine '14fashion, yielding 26 grams of a material which Tetramethylhexamethylenediamine 0. was liquid at steam bath temperature but whichcrystallized slowly on standing. This compound It will be understoodthat the above tests are has the following structure: given forillustrative purposes only and that my cinio-c-oH=cNn-cn,oH-cH1NH-c=cn-c-o cam H: H HaN,N-(2-hydroxy-trimethyiene)-di-(ethy1-beta-amino-crot0natc) 14.6 gramsof triethylene tetramine were mixed invention is not to be limitedthereto. Various with 26 gramsof ethyl acetoacetate and treated otheresters and amides of other N,N'-allwleneas in the preceding exampleleaving 33'grams di(beta-amino-crotonic) acids coming within of a redliquid which contained 14.4% nitrogen. my invention may be employed. Forexample,

The compound has the structure: other suitable beta-ketonic acids, whoseesters u n C:HaOQCH=CNHCHa-GHz-NH-CHr-CHz-NH-CHz-CHr-NHC=CHCO(31H;

CH: V H.

N,N'-(3,6-diaza-octamethylene)-di-(ethyl-betmmlno-crotonato) Theeffectiveness of the above compounds as and amides can be used in thepreparation of color stabilizers was determined by dissolving compoundsof my invention, are: 0.2% of each in grams of a naphthene base SAE oilcontained in 50 cc. beakers. A small acetoaceuc acid piece ofautobodysteel /2" x was added H to each beaker and the whole immersed in anoilbath for 6 hours at 150 Cl Color changes alpha methyl beta ketobutyrlc acid the per cent color increase calculated for each 0 oil. Theresults are as follows. Percent I I 0 0H Compond added to oil: colorincrease b t k t acid None -control 376N,N'-(beta,beta'-1,4-diethylphenylene) u di-(ethyl-beta-amino-crotonate) 4'7 N,N' (3,6 dioxa octamethylene) -di-CHPwHflFC CHPCOOH (ethyl-beta-amino-crotonate) 84 beta-keto-valeric acidN,N' (2 hydroxy trimethylene) di- 0 (ethyl-beta amino-crotonate) 42 ("JN,N' (3,6 diaza octamethylene) -'di- CHr-CHP 43111-0003(ethylqbeta-ammo-cmtonate) 108 alpha-ethyl-beta-keto-hexanoic acid Inorder to show the superiority of my como CHPCH; pounds over compounds ofsomewhat similar g 1 type disclosed in the prior art, comparative testsB' were performed. In these tests, the color read- 5alpha-phenyl-beta-keto-valeric acid ing on the heated oils was convertedto true color units and the percent inhibition in color O formation inthe oil brought about through the I 0 I use of these compoundswascalculated on this P; basis. Employing'such procedure. a comparisonof the efl'ecti'veness of the compounds of my inbeta-kete-octanoie acidvention with other known derivatives of diamines is given in Table IV.All compounds were ll employed in 0.1% concentration in a naphthenicCHP(?H) C CHCOOH base SAE 30 oil. The ester and amide groups may haveany hydrocarbon radical bonded to the oxygen or nitrogen thereof.Preferably, the hydrocarbon radical, bonded to the oxygen of the estergroup, contains only 2 to 5 carbon atoms, that is, X in the formularepresents the radical of an alcohol of 2 to 5 carbon atoms. Suitablehydrocarbon radicals are:

Ethyl Methyl-n-propyl methyl Propyl Methyl isopropyl methyl IsopropylDimethyl ethyl methyl Butyl Amyl Isobutyl Isoamyl Sec. butyl Allyl Tert.butyl Benzyl 3 methyl butyl Phenyl 2-methyl butyl. Diphenyl Diethylmethyl Tert. butyl methyl and the like.

Amongst the other aliphatic diamines which may be reacted with suchesters and amides, I have found the following to provide particularly2-ethyl-hexyl 2-methyl-pentyl .suitable compounds:

While, in the above tests, my compounds have been added to refined oils,they can be added to unrefined oils or to the oils at any suitable stagein the refining process wherein they may serve to stabilize the oils andbe carried through the refining operations with the oils. They may beadded in very small quantities during each of the various stages of therefining processes.

They may be included with the refining agent as in solvent extractionprocesses, and through such medium be transferred into the oil. They mayalso be added to oils of synthetic origin which are substantially of thehydrocarbon type such as are derived from polymerized olefines,hydrogenation of carbon oxides, reaction products of chlorinated waxesand aromatic hydrocarbons. or polymerized cracked waxes.

From the above disclosure, it will be apparent that, by my invention, ithas been made possible to produce viscous mineral oils of high colorstability, particularly under conditions of exposure to heat and .light.

This is a continuation-in-part of my copending application Serial No.299,259 filed October 13, 1939. 1

I claim:

1'. A viscous petroleum oil normally tending to deteriorate in colorhaving incorporated therein a small proportion, suilicient to materiallyinhibit such deterioration, of adi-ester of an-N,N-ethylene-di(beta-amino-crotonic) acid which, except ior the N of theamino groups and the O of the ester groups, consists of carbon andhydrogen.

2. A viscous petroleum oil normally tending to deteriorate in colorhaving incorporated therein a small proportion, suflicient to materiallyinhibit such deterioration, of a di-ester of N,N'-ethylene-di)beta-amino-crotonic) acid which, except for the N of theamino groups and the O of the ester groups, consists of carbon andhydrogen.

3. A viscous petroleum oil normally tending to deteriorate in colorhaving incorporated therein a small proportion, sufficient to materiallyinhibit such deterioration, ofN,N-ethylene-di(ethylbeta-amino-crotonate) 4. A viscous petroleum oilnormally tending to deteriorate in color having incorporated therein asmall proportion, suflicient to materially inhibit such deterioration,of N ,N-hexamethylenedi(ethyl-beta-amino-crotonate).

' 5. A viscous petroleum oil normally tending to deteriorate in colorhaving incorporated therein a small proportion, suflicient to materiallyinhibit such deterioration, ofan N,N'-alkylenedi(alkyl-beta-aminocrotonate) which, except for the Not the amino groups and the O of theester groups, consists of carbon and hydrogen and in which the alkylgroup contains from 2 to 5 carbon atoms. I

6. A viscous petroleum oil normally tending to deteriorate in colorhaving incorporated therein a small proportion, sufiicient to materiallyinhibit such deterioration, of an N,N'-propylenedi(alkyl-beta-aminocrotonate) which, except for the N of the amino groups and the O of theester groups, consists of carbon and hydrogen and in which the alkylgroup contains from. 2 to 5 carbon atoms.

7. A viscous petroleum oil normally tending to deteriorate in colorhaving incorporated therein a small proportion, suiiicient to materiallyinhibit such deterioration, of an unsubstitutedN,N'-'propylene-di(alkyl-beta-amino crotonate) in which the alkyl groupcontains from 2 to 5 carbon atoms.

8. A viscous petroleum oil normally tending to deteriorate in colorhaving incorporated therein a small proportion, suiflcient to materiallyinhibit such deterioration, of N,N'-propylene-di(ethylbeta-aminocrotonate).

9. A viscous petroleum oil normally tending to deteriorate in colorhaving incorporated therein a small proportion, suflicient tomaterially-inhibit such deterioration, of a compound of the groupconsisting of di-esters and amides of organic acids having twobeta-amino-crotonic acid residues linked through the beta-amino nitrogenatoms to separate carbon atoms of a single divalent aliphatic radicalcontaining from 2 to 10 carbon atoms, which compound is free of acidicgroups other than the crotonic acid carboxyl group.

10. A viscous petroleum oll normally tending to deteriorate in colorhaving incorporated therein a small proportion, suflicient to materiallyinhibit-such deterioration, of a di-ester of an organic acid having twobeta-amino-crotonic acid residues linked through the beta-amino nitrogenatoms to separate carbon atoms of a single divalent aliphatic radicalcontaining from 2 to 10 carbon atoms, which compound is free of acidicgroups other than the crotonic acid carboxyl group.

1 1. A viscous petroleum oil normally tending to deteriorate in colorhaving incorporated therein a small proportion, sufllcient to materiallyinhibit such deterioration, of a di-ester of an amsubstitutedN,N'-a.1ky1ene-di(beta-amino-crotonic) acid which is free of acidicgroups other than the crotonic acid carboxyl group and in which thealkylene group contains from 2 to 10 carbon atoms.

12. A viscous petroleum oil normally tending to deteriorate in colorhaving incorporated therein a. small proportion, suflicient tomateriallyinhibit such deterioration, of'anN,N'-alkyienedi(ethyI-beta-amino crotonate) which, except for the N ofthe amino groups and the O of the ester groups, consists of carbon andhydrogen and in which the alkylene group contains from 2 to 10 carbonatoms.

MELVIN A. nrm'mcn.

